All it takes is 75 minutes a week of physical activity to extend your life by nearly two years past age 40, according to U.S. researchers -- and there are benefits regardless of body weight. So listen up, "healthy" couch potatoes.

The study by the U.S. National Cancer Institute also suggests that regular activity would boost life expectancy even more. It showed that just over 10 minutes a day of exercise was associated with 1.8 years of added life expectancy, compared to getting no leisure-time activity.

Brisk walking for 450 minutes a week, just over an hour a day, was associated with living 4.5 more years longer.

Read the news release at NIH.